Memory devices are common in electronic systems and computers to store data. These memory devices may be volatile memory, where the stored data is lost if the power source is disconnected or removed, or non-volatile, where the stored data is retained even during power interruption. An example of a non-volatile memory device is the programmable metallization cell (PMC) that is also known as a conductive bridging RAM (CBRAM), nanobridge memory, or electrolyte memory.
A PMC utilizes an ion conductor such as a chalcogenide type or an oxide type and at least two electrodes (e.g., an anode and a cathode) with the ion conductor between the electrodes. When a voltage is applied across the electrodes, superionic clusters or conducting filaments rapidly grow from the cathode through the ion conductor towards the anode. This gives rise to a low resistance state. When an electric field of opposite polarity is applied across the electrodes, the conducting filaments dissolve and the conducing paths are disrupted. This gives rise to the high resistance state. The two resistance states that are switchable by the application of the appropriate electric field are used to store the memory data bit of “1” or “0”.
An exemplary PMC utilizes germanium selenide with silver ions diffused therein. Current methods provide silver ions within the germanium selenide material by initially depositing the germanium selenide glass layer onto a substrate, typically a first electrode, and then depositing a thin overlying layer of silver, typically by physical vapor deposition (i.e., sputtering). The thin silver layer can then exposed to electromagnetic energy such as ultraviolet (UV) radiation to diffuse silver into the germanium selenide layer, such that a homogenous distribution of silver throughout the layer is ultimately achieved. The upper electrode can then be formed from silver that is sputter deposited onto the metal-doped germanium selenide layer.
However, the formation of the silver electrode is wrought with drawbacks. For example, issues of adhesion, agglomeration and non-uniform thickness plague the formation of the silver electrode for the PMC. Therefore, a need exists for a PMC construction and processes for fabricating PMC that avoids such problems.